Heretofore in self-loading and automatic or semiautomatic firearms designed to fire high-powered ammunition it has been necessary to utilize a mechanically locked breech. Such systems are present in most gas or recoil operated firearms and require somewhat complicated breech and locking mechanisms in which the tolerances of the various components are critical. Not only are such weapons more difficult and expensive to manufacture but because of the close tolerances wear on the parts and subsequent replacement is often required. In addition, because of the multiplicity of the components, such weapons are quite heavy and thus somewhat burdensome for an operator to carry and handle.
A number of simplified self-loading and automatic or semi-automatic weapons have been proposed in attempts to obviate the disadvantages of mechanically locked breech operated weapons known as blowback firearms, which because of their ease of maintenance, relatively few parts and lower cost, have been used extensively for military purposes. However, such weapons have necessitated the use of relatively low-powered ammunition since the gas expanding in the firing chamber cannot reach great enough pressure before the action of the rearward moving breech results in significant pressure drop in the firing chamber. Accordingly, the velocity of the bullets fired from such weapons is relatively low and concomitantly the accuracy is significantly impaired by the heavy breech block being in motion compared to weapons incorporating mechanically locked breeches.
In an attempt to overcome this problem, mechanically delayed blowback weapons have been proposed which incorporate roller locks or similar devices. However, such weapons have proven extremely expensive to manufacture because of very close tolerances required in the action as well the complicated multi-piece breech blocks needed for the delay system. Gas operated blowback devices for damping or delaying recoil of the breech or bolt have been proposed, for example, in U.S. Pat. Nos. 1,834,021 and 3,261,264. However, such devices do not provide for adequate damping of the breech block or bolt during the delayed recoil. Moreover, these prior art devices do not adequately provide for venting of the hot gases from the locking chamber. Unless these gases are adequately removed, the weapon may soon overheat to an extent of malfunction as well as causing possible permanent deterioration of the components involved.